So Littman and Bailey are controversial. Not unethical. (Fyi Lisa Littman is herself a trans woman).

Incorrect. They are both unethical.

Littman for example, when doing her study on rapid onset gender dysphoria, targeted only online spaces which were full of parents that were upset and angry at having a transgender child. Her sample was deliberately and knowingly biased towards supporting the hypothesis she invented. Her audience also didn't involve any trans people, only the parents of trans people, and parents who were, as a group, explicitly more likely to be strongly uncomfortable with the idea of having a trans child.

This wasn't a mistake, or an oversight. It was a deliberate choice she made to bias her results. That's not "controversial", that's outright unethical.

Similarly, Bailey regularly lies to his participant audience, and loads his studies with questions predisposed to get the results he wants to show.

The study linked to in this post is a classic example of that. None of the results of this will be designed to help people navigate dysphoria. The study is trying to draw trans people in to think that they're helping, when in fact, the results will be used to actively undermine their ability to seek transition care and support.

Bailey and Littmans findings make the trans community angry because the research supports that for some trans females, (not all but some) they transition due to a sexual kink. That they can only be sexually excited by being a woman.

Even that's not true.

When you look at the definitions Bailey uses for autogynephilia for example, if you apply those same measures to cis women, it turns out, they too more often than not, meet the requirements for autogynephilia. It only becomes a paraphilia when the woman is trans though, and it only becomes an explanation for the woman's identity, when the woman is trans.

It's taking a real correlation, ignoring the fact that the correlation isn't unique to trans folk, and then using that correlation as an explanation for trans identity.

He never said it's true for all female trans people.

He said it's the only way to be a trans woman that is asexual, bisexual or gay.

The only trans women who don't fit his criteria of transitioning due to a paraphilia, are straight trans women. Who, by the way, he calls "Homosexual transexuals". He can't even recognise their gender... And speaking of that, even though he thinks that trans women who aren't straight should be able to transition, he doesn't think that they're women, and will repeatedly misgender them or talk only about their birth sex when talking about them.

Take a look at this, from his personal blog...

In this screenshot, you can see that whilst defending a woman who had nazis at her rally, he refers to trans women as "male" without ever referring to them as women, whilst also showing a diagram that says all trans activists are paraphillic (and thus, not really trans)

Bailey genuinely believes he is doing good science. But he's not. He's got a lens through which he perceives transgender identity, and he is absolutely not open to challenging that. That's not good science...

I struggle to understand how you can call anything the man does "ethical"